SDR Advantages and Disadvantages

For those unfamiliar with software defined radio and related topics, here's a great tutorial by VT. The slide set does a good job in defining SDR by showing how the physical layer is moved from hardware into software and how the radio adapts to its environment although that part leans more to the Cognitive Radio side. The advantages of SDR include reduced component cost because hardware specific components are replaced by DSPs and FPGAs. The number of components tends to be lower. DSP components can compensate for problems in other areas of the system. Disadvantages include power consumption, security, and overall cost.

The key difference between traditional radios and software defined radios is that the latter senses their environment and adapt to it. This is important particularly to government agencies such as the FCC who is in the process of reallocating spectrum usage in the TV bands. There's a shift away from rigid, spectrum allocations to a demand-based approach to maximum the usage in that band. Currently, spectrum usage in most bands in the USA range from .3 to 3%. As the need for more spectrum grows, a new paradigm will be needed to supply this bandwidth.

Best regards,

Hall T.

Using SDR in Pico Satellites

Software defined radio is not just for mobile phone communications. It finds applications in numerous other places and for different reasons. One of the more intriguing applications is that in pico satellites. Pico satellites are small satellites developed by university groups for research and education purposes which catch a ride on rocket and space shuttle flights. Once out of the earth's atmosphere, they are tossed out into the ether and start their mission. In this application SDR is used for positioning and navigation. By using SDR techniques, the positioning system was made lighter, smaller, and most importantly with lower power consumption.

Best regards,

Hall T.

Power Management in SDR

SDR brings a great deal of resource-intensive processing to the application in order to handle the variety of waveforms, modulation schemes, and other RF functions. This additional processing comes at the expense of greater power requirements. This drives the designer to make performance/power tradeoffs in the design of SDR systems. Power management in Software Defined Radio is a major concern since most SDR applications use more power than hardware radios. Also, field deployed units need to conserve power since they typically run on batteries. The RF front ends are typically overpowered as they need to generate RF patterns across a wide range. Finally, SDR applications tend to generate excessive heat which needs to be dissipated.

Power management is a key success factor in software-defined radio applications due to the portable nature of most target systems. In this paper the authors propose a horizontal layering of the hardware along with software-specific APIs to provide component-level control over power management. By dividing the system into components, power consumption can be customized for the application. For example, a signal processing intensive application could shut down other functions while the FPGA/Processor works. The user can turn off functions to increase the battery lifetime in a mission critical operation.

Best regards,
Hall T.